The present invention relates to an interior image receiving apparatus for receiving the image of an inner surface of a hollow object, such as a flange of an aluminum can, through the opening of the object. This application is based on patent applications No. Hei 8-282688 and No. Hei 9-017146 filed in Japan, the contents of which are incorporated herein by reference.
Large aluminum cans are increasingly being used instead of small cans, because of larger capacity. Although the inner diameter of the middle of the body of the can is large, the top of the body is narrowed. As shown in FIG. 7, the aluminum can 1 comprises a cylindrical body 2 having a closed bottom, and a flange 3 which is narrowed toward the upper opening. Although the flange 3 was formed of a number of steps parallel to the top face, it is recently formed as a curved surface.
When the curved flange 3 is formed in the manufacturing process, defects such as wrinkles (pleats) may occur because the top of the aluminum can is narrowed. An interior image receiving apparatus is used in order to detect the defect on the inner surface of the aluminum can 1. An inner image of the body of the aluminum can 1 can be obtained with a camera of the interior image receiving apparatus using a fisheye lens. However, it is impossible to obtain the image of the inner surface of the narrow flange 3.
In order to obtain the image of the inner surface of the narrow flange 3 in mass production, a camera and an illuminating means are inserted into the aluminum can, and are rotated, receiving an image of the inner surface of the aluminum can 1. Based on the image, an image processing device detects a defect on the inner surface of the aluminum can, which is thereafter removed from the production line. However, because such an interior image receiving operation takes a substantial amount of time, it is impossible to rapidly produce aluminum cans.